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Bad bugs: The worst disasters caused by software fails

Clever software can make our lives easier but a glitch can have disastrous consequences. In the past decades, computer bug catastrophes have caused deaths and disrupted lives on a large scale. Sally Adee takes us through six major software fails.

Space: Ariane 5

On June 4 1996, the European Space Agency test-launched the Ariane 5 rocket. A bug in the control software, written in the programming language Ada, caused the rocket to self-destruct 37 seconds after blast-off.

(Image: ESA)

Money: Knight Capital

Last year, a computer glitch nearly pushed investment firm Knight Capital into bankruptcy. The firm lost half a billion dollars in half an hour when a software error allowed computers to buy and sell millions of shares with no human oversight. The company's stock prices plunged by about 75 per cent in two days.

(Image: Brendan McDermid/Reuters)

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Medical: Radiation therapy

In the 1980s, five patients died after receiving a massive dose of X-rays, the result of a programming bug in a Therac-25 radiation therapy machine. The disaster is thought to have been caused by a glitch that made separate code threads try to do the same thing at the same time.

(Image: Universal Images Group/Getty)

Your online stuff: Amazon crash

The outage of Amazon servers last summer separated many people from their cloud storage. The downtime – originally caused by an electrical storm – was extended by previously unseen programming bugs. The scale at which cloud providers operate makes them vulnerable to cascading failures. Almost all online users now use cloud computing in some way – whether for webmail, storing photos or when using social media – which raises issues about the safe storage of digital possessions.

(Image: Kristoffer Tripplaar/Sipa/Rex Features)

Infrastructure: The north-east US power outage

The 2003 North America blackout, at the time the second most widespread power outage in history, was the result of a local blackout that went undetected then cascaded out of control. General Electric Energy's monitoring software was affected by the same type of software problem that caused the X-ray disaster in the 1980s.

(Image: Spencer Platt/Getty Images)

Transport: American Airlines

Earlier this year, a software bug grounded the entire American Airlines fleet. A glitch in the company's Sabre reservation system was introduced after two existing systems were patched together following the merger of several airlines. The problems probably arose from trying to combine platforms written in different programming languages.